During semiconductor manufacturing process, defects such as particles and scratches on the surface of a semiconductor wafer may lead to malfunctions such as poor insulation or a short of wiring formed on the wafer surface. Along with finer design rules for circuit pattern, smaller defects may cause poor insulation of a capacitor as a patterned element and failures in a gate oxidation film or the like. Defects on a semiconductor wafer prior to the formation of a circuit pattern, i.e., on the surface of a bare wafer similarly affect electrical characteristics of the circuit pattern formed later. That is, it is important for semiconductor manufacturing process to detect a defect on a semiconductor wafer as a substrate for each step and to feed back such a defect to the related manufacturing steps.
Such a defect on a substrate such as a semiconductor wafer is detected by an inspection tool. An example of such a type of inspection tools includes an optical inspection tool configured to irradiate the substrate surface with light (inspection light) and detect scattered light generated from the irradiated substrate surface, and detect a defect on the substrate based on a result of the detection.
This type of inspection tool used as a defect inspection tool to inspect a defect on a semiconductor wafer, for example, is roughly classified according to the usage into a surface inspection tool to inspect a defect on a bare wafer such as a mirror-surface wafer having a surface subjected to mirror finish by polishing process, and a pattern inspection tool to inspect a defect on a patterned wafer with a circuit pattern formed thereon.
For both of these surface inspection tool and pattern inspection tool, inspection tools are configured to detect scattered light generated from an illumination spot on a substrate that is irradiated with light by an optical detector, thus obtaining a detection signal of the scattered light corresponding to the amount of detection. The optical detector used in such a configuration is an imaging device having multiple sensor pixels. They may be configured to move and/or revolve a substrate as an inspection sample, thus scanning the illumination spot on the substrate irradiated with the light.
Such a type of inspection tools and imaging devices as conventional techniques are described in Patent Literatures 1 to 4.